Abstract: The resistance of plants to metals includes avoidance and tolerance, while the organic acids with chelating ability in plants play an important role in the detoxification of metals both externally and internally. In the external metal detoxification, plant roots excrete organic acids into rhizosphere, and the metal pollutants are detained outside the roots by the formation of metal organic acid complex. In the internal metal detoxification, the metal pollutants in cytosol are chelated with the organic acids, and their toxicity is reduced. The formed organic acids in plants are differed with plant species and metal pollutants.

Key words: Spinacia oleracea, Nitrogen supply, Nitrate, Vitamin C, Oxalate, Antioxidative enzyme activities, Proline